How do the No people win in this scenario? What happens if Markdown is added and GDP goes down? How do you resolve that markdown actually caused the change in

How do the No people win in this scenario? What happens if Markdown is added and GDP goes down? How do you resolve that markdown actually caused the change in GDP? (Aren't you just asking people to conditionally bet on GDP going up?) Who are people betting against if No loses? (Who's money do they get?)